This section provides background information relating to the present disclosure, which is not necessarily prior art.
In Release 10 (R10) of a Long Term Evolution-Advanced (LTE-A) system, channel state information reference signals (CSI-RSs) are introduced to acquire channel state information. Beamforming is a signal preprocessing technology based on an antenna array, in which, a weighting coefficient of each array element in an antenna array is adjusted to generate a beam with directivity, thereby obtaining an obvious array gain. Therefore, beamforming has advantages in broadening a coverage, improving an edge throughput and interference suppression and so on. Therefore, a beam-formed CSI-RS scheme may function as an enhanced CSI-RS transmission scheme.
However, there are some problems when the beam-formed CSI-RS scheme is adopted. In the LTE-A system, neighboring cells use the same time and frequency resource. Therefore, in a case that a service cell and a neighbor cell transmit beam-formed CSI-RSs by using the same CSI-RS resource and cell cooperation is not supported, great interference occurs. In the existing beam-formed CSI-RS transmission, beamforming for eight ports is supported, and there are five types of resources for CSI-RS transmission, therefore neighboring cells can transmit beam-formed CSI-RSs by using different resources, thereby substantially avoiding interference between beam-formed CSI-RSs. However, in a future LTE-A system, there may be more than eight ports, such as sixteen ports. In addition, cells will become more intensive. In a case that the number of neighboring cells of the service cell is greater than four, five types of CSI-RS resources are not sufficient to avoid the interference between beam-formed CSI-RSs. In the other hand, beamforming is generally performed for users at an edge of the cell, therefore a transmitting power is great; and once the neighboring cells transmit beam-formed CSI-RSs by using the same CSI-RS resource, severe interference occurs. In another aspect, in the service cell, certain interference occurs in a case that beam-formed CSI-RSs are transmitted to two user equipments by using the same CSI-RS resource.
Therefore, for at least one of the above problems, it is necessary to provide a new wireless communication technical solution, so as to solve the interference between beam-formed CSI-RSs and improve the performance of a system.